APPLIED: [B][C][SRU][PATCH 0/1] Fix for ftrace test hang issue

[Khaled Elmously]

On 2019-05-07 16:50:05 , Po-Hsu Lin wrote:
> BugLink: https://bugs.launchpad.net/bugs/1826385
> 
> == Justification ==
> Running the ftrace in ubuntu_kernel_selftests repetitively against x86
> Cosmic kernel will cause system hang.
> 
> When this happens, you won't be able to ssh into this system, and no log
> can be found in syslog.
> 
> This hang is caused by one of the sub-test: kprobe/multiple_kprobes
> 
> Masami's comment from upstream discussion (https://lkml.org/lkml/2018/12/3/1219):
> In arch/x86/kernel/kprobes/opt.c, copy_optimized_instructions() does a
> copy loop, but only update src and dest cursors, but not update real
> address which is used for adjusting RIP relative instruction.
> 
> == Fix ==
> 43a1b0cb4 (kprobes/x86: Fix instruction patching corruption when copying
> more than one RIP-relative instruction)
> 
> This patch is already in D.
> For B/C, they all have this ill-commit 63fef14 and this patch can be
> cherry-picked. Note that for Bionic kernel it can only be triggered in
> this way with a kernel built with GCC-8.
> 
> Although it's a bit difficult to trigger this on Bionic, I think it
> worth this fix as it's quite straightforward.
> 
> For X, the ill-commit 63fef14 does not exist.
> 
> == Test ==
> Test kernel for Cosmic and Bionic built with GCC-8:
> http://people.canonical.com/~phlin/kernel/lp-1826385-ftrace-hang/
> 
> (To verify this for the Bionic, you will need to build a kernel with GCC-8.)
> 
> Patch tested with a bare-metal and a KVM node, both of them can pass the
> beating repetitively.
> 
> == Regression Potential ==
> Low, upstream fix specific for kprobe and limited to x86 architecture.
> 
> 
> Masami Hiramatsu (1):
>   kprobes/x86: Fix instruction patching corruption when copying more
>     than one RIP-relative instruction
> 
>  arch/x86/kernel/kprobes/opt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> -- 
> 2.7.4
> 
> 
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